body {
    margin:0 auto;
    width: 100%;
}
.main {
    width: 50vw;
    height: 50vh;
    position: relative;
    margin:0 auto;
    background-color: red;
}
.wrap {
    position: absolute;
    width:50%;
    height:50%;
    top: 10vh;
    left: 0;
    background-color: blue;
}